1. Field of the Invention
The present invention relates to an internal combustion engine provided with a camshaft holder rotatably supporting a camshaft or camshafts included in a valve train and attached to a cylinder head, and an accessory or auxiliary machinery rotatively driven by the camshaft and, more specifically, to the construction of an accessory holder mounted on the camshaft holder to hold an accessory.
2. Description of the Related Art
In an internal combustion engine provided with an accessory rotatively driven by a camshaft included in a valve train, the accessory is attached to a mounting seat formed on a cylinder head, on which a camshaft is supported for rotation, with its driving shaft interlocked with the camshaft passed through a through hole formed in the mounting seat. Such an arrangement is disclosed in JP-A 2000-80968.
The mounting seat for the accessory driven by the camshaft additionally formed in the cylinder head which is integrally provided with a camshaft support part for supporting the camshaft enlarges the cylinder head. Such a cylinder head formed by casting is likely to have a dead material and a large weight. The mounting seat formed integrally with the cylinder head protrudes upward from the joining surface of the cylinder head to which the joining surface of the cylinder head cover or valve cover is joined. Therefore, much finishing work needed to form the joining surface accurately increases the manufacturing cost of the cylinder head.
If torque necessary for rotating the camshaft is caused to vary by the operation of the accessory, it is desirable not to promote the variation of the torque resulting from the valve opening operation of the valve train for opening the valves of the internal combustion engine.